Self-quenched superregenerative receiver



Patented Sept. 10, 1946 SELF-QUENCHED SUPERREGENERATIVE RECEIVER EdmundE. Birr, Kenmore, N. Y., assignor to Colonial Radio Corporation,Buffalo, N. Y.

Application June 29, 1944, Serial No. 542,713

Claims.

This invention relates to superregenerative receivers, and moreparticularly to superregenerative receivers of the self-quenched type.

In the past, considerable difliculty has been encountered inself-quenched superregenerative receivers due to interference betweenhigher harmonics of the quenching frequency and the si nal to bereceived. This effect may limit the low frequency range of suchreceivers when a high order of sensitivity is desired.

The interference can occasionally be overcome by a selection of quenchfrequency such that the strongest harmonics of the quench frequency areoutside the tuning range, but this method is frequently unsatisfactoryif the receiver is required to cover a wide range of frequencies.

Also, in quantity production 'of such receivers the effect is likely tobe different from receiver to receiver, making it necessary to changethe quench frequency in each individual case.

It is frequently found also that there is no possible adjustment ofquench frequency which will eliminate the trouble, even when thequenching frequency is lowered so far that the audio response limit ofthe receiver is approached.

In accordance with my invention, I have found that this difficulty canbe eliminated by the use of a special resistor or resistance capacitynetwork in the receiver circuit, aswill be more .par-- ticularlyexplained hereafter.

It is an object of my invention to provide a superregenerative receiverof the self-quenched type which is not subject to the interference andundesired effects above mentioned.

It is a further object of my invention to elimihate the above mentionedinterference and undesired eliects without impairing the sensitivity ofthe receiver.

It is a further object of my invention to eliminate the saidinterference and undesired effects without impairing the selectivity ofthe -receiver.

Still other objects and advantages of my invention will be apparentfrom. the specification.

The features of novelty which I believe to be characteristic of myinvention are set forth with particularity in the appended claims. Myinvention itself, however, both as to its fundamental principles and asto its particular embodiments, will best be understood by reference tothe specification and accompanying drawing, in which Fig. 1 shows oneform of my invention as applied to a self-quenched, superregenerativereceiver.

Fig. 2-shows another way of applying my invention to the same receiver.

Fig. 3 shows my invention applied to a receiver utilizing a differenttype of feed-back circuit.

Fig. 4 indicates a resistance of the type employed in my invention.

Figs. 5 and 6 illustrate alternate forms of resistance capacity networkswhich may be employed with my invention.

In the various figures like reference characters indicate like parts.

Referring now more particularly to Fig. 1, I have indicated asuperregenerative receiver of the self-quenched type employing a tunedcircuit consisting of inductance .Ill and variable condenser I I. Thedetector and oscillator tube is indicated as I2, and may comprisecathode I20, control grid I29, and anode I2a.

Control grid IZg may be connected through condenser I3 to one terminalof tuning condenser I I, cathode He may be connected to ground, andanode I211 may be connected to the opposite terminal of condenser I I. Amidpoint or a suitable intermediate point of the inductance l0 may be'connected through the primary of audio transformer I5 to the +13 supplyand through bypass condenser M to ground.

The circuit will be recognized as an oscillator of the Well-knownHartley type, and when operated with a suitable resistance betweenterminals A and B respectively connected to the grid I2g and to anode I2a, and when the resistance and the value of condenser I3 are properlychosen, the circuit will operate as a self-quenched, superre generativereceiver and will operate as a detector for incoming signals, which maybe supplied to the tuned circuit I6 and II through any suitable means(not shown).

As already stated, such a receiver is subject to interference betweenharmonics of the quench frequency and the incoming signal. I havediscovered that this difficulty can be eliminated if the resistancewhich is connected between the terminals A and B has a characteristicsuch that its resistance is relatively high at the quench frequency andrelatively low at the desired signal frequency.

Certain resistance on the market have such a characteristic, which isordinarily regarded as undesirable, and which would'ordinarilyberegarded as sufficient reason for preventing their use in such circuits.However, I find that such resistances when employed in a circuit of thistype, eliminate the interference and other undesired effects quiteremarkably. In Fig. 4 I have indicated resistance I8 as of this type, inwhich the value of the resistance decreases as frequency increases.

In Fig. 5 I have shown an alternative form consisting of resistances I9and 24 in series, which, in this instance, may have a substantially flatfrequency characteristic, and resistance 19 may be shunted by acondenser 20, which offers a high impedance at quench frequencies andrelatively low impedance at desired signal frequen-cies.

In Fig. 6 I have indicated still another alternative form, this being anetwork consisting of resistances 2! and condenser 22 in series, bothshunted by resistance 23. In this instance both resistances 2i and 23may have a fairly flat frequency characteristic, and the entire networkis so chosen that the impedance at quench frequencies is relativelyhigh, and at desired signal frequencies is relatively low. Any one ofthe circuits indicated in Figs. 4, 5, and 6 may be connected betweenpoints A and B of Fig. 1, 2, or 3.

Referring now more particularly to Fig. 2, this shows the same circuitas in Fig. l, but in the present instance the network terminals A and Bare connected between grid and cathode instead of between grid andanode. The operation of the circuit is essentially the same.

Referring now more particularly to Fig. 3, there is shown a conventionaltype of feed-back circuit consisting as before of inductance I 0 andcondenser !l, detector tube I2, having a cathode 120, control grid I29,and anode Ho, and in this instance employing a feed-back coil llinductively related to the inductance I0 and connected to the anode i2aand to the anode side of the audiofrequency transformer 15, which inturn is connected to the +73 supply, the transformer i5 being shunted inthis case by by-pass. condenser 16.

In this instance the resistance capacity network may be connectedbetween grid I2g and ground, and the operation of this circuit inrespect of superregeneration, selfiquenching, and the elimination of theabove mentioned interference and other undesired effects, is the same asbefore.

While the exact operation of such circuits is not completely understoodin respect to theory, and while I do not, therefore, wish to be bound byany particular theory as to why my invention operates as it does, Ibelieve that the lower value of the resistance at desired signalfrequencies lowers the Q of the input circuit to some extent and thatthis lowering of the Q. reduces the amplitude of the higher frequencyharmonics of the quench frequency to such an extent that the trouble isgreatl reduced or even entirely eliminated. At the same time, thesensitivity and selectivity of the receiver is not measurably impaired.At any rate, whether this theory be correct or not, there is no doubt asto the facts.

For the purpose of completing the disclosure herein, and not by way oflimitation, the following values are given: resistance I8 isapproximately 1 megohm D. C. at quench frequencies and approximately100,000 ohms at incoming signal frequency; resistance 2 90,000 to100,000 ohms; resistance l9, approximately 900,000 ohms; condenser 20,10 rnmf.; resistance 2!, 90,000 to 100,000 ohms; resistance 23, 1megohm; and condenser 22, 10 mmf.

While I have shown and described certain preferred embodiments of myinvention, it will be understood that modifications and changes may bemade without departing from the spirit and scope thereof, as will beclear to those skilled in the art.

' In this application I have particularly pointed out and distinctlyclaimed the part, improvement, or combination which I claim as myinvention or discovery, and I have explained the principles thereof andthe best mode in which I have contemplated applying those principles soas to distinguish my invention from other inventions.

I claim:

1. In a superregenerative receiver of the selfquenching type, incombination, a tuned circuit, a thermionic vacuum tube connected theretohaving an anode, a cathode, and a control electrode, and a resistanceconnected between the control electrode and one of the other electrodesof said tube, said resistance having a relatively high value at quenchfrequencies and a relatively low value at desired signal frequencies.

2. In a superregenerative receiver of the selfquenching type, incombination, a tuned circuit, a thermionic vacuum tube connectedthereto, having an anode, a cathode, and a control electrode, and aresistance connected between the control electrode and one of the otherelectrodes of said tube, said resistance having a relatively high valueat quench frequencies and its resistance decreasing at a substantialrate with frequency increase.

3. In a superregenerative receiver of the selfquenching type, incombination, a tuned circuit, a thermionic vacuum tube connectedthereto, said tube having a cathode, an anode, and a control electrode,and a resistance-capacity network connected between said controlelectrode and one of the other electrodes of said tube, said networkhaving a high impedance at quench frequencies and a relatively lowimpedance at desired signal frequencies.

4. Ln a superregenerative receiver of the self quenching type, incombination, a tuned circuit, a thermionic vacuum tube connectedthereto, said tube having a cathode, an anode, and a control electrode,and a resistance-capacity network connected between said controlelectrode and one of the other electrodes of said tube, said networkcomprising a resistance and capacity in parallel and a resistance inseries therewith and having a high impedance at quench frequencies and alow impedance at desired signal frequencies.

5. In a superregenerative receiver of the selfquenching type, incombination, a tuned circuit, a thermionic vacuum tube connectedthereto, said tube having a cathode, an anode, and a control electrode,and a resistance-capacity network connected between said controlelectrode and one of the other electrodes of said tube, said networkcomprising a resistance and capacity in series shunted by a resistance,said network having a high impedance at quench frequencies and arelatively low impedance at desired signal frequencies.

EDMUND E. BIRR.

